Swiftui Performance Audit

1. Intake

Collect:

• Target view or feature code.
• Symptoms and exact reproduction steps.
• Data flow: @State, @Binding, environment dependencies, and observable models.
• Whether the issue shows up on device or simulator, and whether it was observed in Debug or Release.

Ask the user to classify the issue if possible:

• CPU spike or battery drain
• Janky scrolling or dropped frames
• High memory or image pressure
• Hangs or unresponsive interactions
• Excessive or unexpectedly broad view updates

For the full profiling intake checklist, read references/profiling-intake.md.

2. Code-First Review

Focus on:

• Invalidation storms from broad observation or environment reads.
• Unstable identity in lists and ForEach.
• Heavy derived work in body or view builders.
• Layout thrash from complex hierarchies, GeometryReader, or preference chains.
• Large image decode or resize work on the main thread.
• Animation or transition work applied too broadly.

Use references/code-smells.md for the detailed smell catalog and fix guidance.

Provide:

• Likely root causes with code references.
• Suggested fixes and refactors.
• If needed, a minimal repro or instrumentation suggestion.

3. Guide the User to Profile

If code review does not explain the issue, ask for runtime evidence:

• A trace export or screenshots of the SwiftUI timeline and Time Profiler call tree.
• Device/OS/build configuration.
• The exact interaction being profiled.
• Before/after metrics if the user is comparing a change.

Use references/profiling-intake.md for the exact checklist and collection steps.

4. Analyze and Diagnose

• Map the evidence to the most likely category: invalidation, identity churn, layout thrash, main-thread work, image cost, or animation cost.
• Prioritize problems by impact, not by how easy they are to explain.
• Distinguish code-level suspicion from trace-backed evidence.
• Call out when profiling is still insufficient and what additional evidence would reduce uncertainty.

5. Remediate

Apply targeted fixes:

• Narrow state scope and reduce broad observation fan-out.
• Stabilize identities for ForEach and lists.
• Move heavy work out of body into derived state updated from inputs, model-layer precomputation, memoized helpers, or background preprocessing. Use @State only for view-owned state, not as an ad hoc cache for arbitrary computation.
• Use equatable() only when equality is cheaper than recomputing the subtree and the inputs are truly value-semantic.
• Downsample images before rendering.
• Reduce layout complexity or use fixed sizing where possible.

Use references/code-smells.md for examples, Observation-specific fan-out guidance, and remediation patterns.

6. Verify

Ask the user to re-run the same capture and compare with baseline metrics. Summarize the delta (CPU, frame drops, memory peak) if provided.

Outputs

Provide:

• A short metrics table (before/after if available).
• Top issues (ordered by impact).
• Proposed fixes with estimated effort.

Use references/report-template.md when formatting the final audit.

References

• Profiling intake and collection checklist: references/profiling-intake.md
• Common code smells and remediation patterns: references/code-smells.md
• Audit output template: references/report-template.md
• Add Apple documentation and WWDC resources under references/ as they are supplied by the user.
• Optimizing SwiftUI performance with Instruments: references/optimizing-swiftui-performance-instruments.md
• Understanding and improving SwiftUI performance: references/understanding-improving-swiftui-performance.md
• Understanding hangs in your app: references/understanding-hangs-in-your-app.md
• Demystify SwiftUI performance (WWDC23): references/demystify-swiftui-performance-wwdc23.md

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.